Set corpusVersion in compilation/test.

This prevents the "object vector is already compiled in this run" error
when testing the Dotty compilation.

Author: olafurpg

compilation/src/test/scala/scala/tools/benchmark/BenchmarkTest.scala

@@ -1,9 +1,15 @@
 package scala.tools.benchmark
 
-import scala.tools.nsc.ScalacBenchmarkStandalone
+import scala.tools.nsc.ScalacBenchmark
 import org.junit.Test
 
 class BenchmarkTest {
-  @Test def compilesOK =
-    ScalacBenchmarkStandalone.main(Array("../corpus/vector", "1"))
+  @Test def compilesOK() = {
+    val bench = new ScalacBenchmark
+    bench.source = "../corpus/vector"
+    bench.corpusVersion = "latest"
+    bench.initTemp()
+    bench.compileImpl()
+    bench.clearTemp()
+  }
 }